red greeen blue are all video. It's a far better quality connection that scart, s-video or the yellow RCA (which is single video) that most TV's and video's have.

Some TV's do have RGB rca plugs on them, and lots of DVD players have them, and I think it a something to do with progressive scan aswell. The idea is that it only carries video signal, and there are three video connections, each one carrying only a major colour group, rather than scart or s-video which carries all three together, along with audio (in scart), or componant (which is the red + white audio RCA's and the yellow (single) video RCA...